Code to generate a unique reference

[matrixpom]

Good day all once again,

I need a code that will generate a unique reference based on a users inputted name, eg. if the name entered in cell "A1" = "John" & the surname in cell "B1" = "Smith", then I need a returned value of "JS1", however if later a new user registers as Jerry Smythe the code will lookup for the same initials & the returned value would then be "JS2", any assistance as always will be greatly appreciated, thank you all & have a great day - Marco

[martindwilson]

you could use in c1 filled down
=IF(A1="","",LEFT(A1)&LEFT(B1)&SUMPRODUCT(--(LEFT($A$1:A1)=LEFT(A1)),--(LEFT($B$1:B1)=LEFT(B1))))